你可以使用像”substring（src_str类似）这样的语法，如果你需要更简单的语法，你可以创建自己的函数，比如：

CREATE OR ALTER FUNCTION F_REMOVE_SPECIALCHARS(
  IN_STR VARCHAR(8000))
RETURNS VARCHAR(8000)
AS
declare variable IN_SIZE integer;
declare variable IDX integer;
declare variable OUT_STR varchar(8000);
begin
  /* Function Text */
  in_size = char_length(IN_STR);
  idx = 1;
  out_str = '';
  while (idx < in_size+1) do
   begin
    if (lower(substring(in_str from idx for 1)) in
                  ('a','b','c','d','e','f','g','h','i',
                   'l','m','n','o','p','q','r','s','t',
                   'u','v','x','y','k','j','@','-','_',
                   '1','2','3','4','5','6','7','8','9',
                   '0',' ')

    ) then
     begin
      out_str = out_str || substring(in_str from idx for 1);
     end
    idx = idx + 1;
   end
  return out_str;
end

在这种情况下，您可以维护所需字符的选择